1. Field of the Invention
Example embodiments of the present invention relate to exposure equipment and an exposure method using the same, and more particularly, to exposure equipment having an auxiliary photo mask and an exposure method using the same.
2. Description of Related Art
A semiconductor device may be manufactured using various unit processes, for example, a photolithography process, an etching process, a thin film deposition process, a diffusion process, and so on. Among the manufacturing processes, the photolithography process directly affects formation of fine patterns on a semiconductor device. Therefore, the photolithography process plays a vital role in the manufacturing of highly integrated semiconductor devices.
The photolithography process may include a coating step of forming a photoresist layer on a semiconductor substrate; an exposure step of selectively irradiating light on a predetermined region of the photoresist layer using a photo mask; and a development step of selectively removing the exposed photoresist layer to form a photoresist pattern.
The exposure step may include aligning the semiconductor substrate having a photoresist layer to a photo mask, irradiating light from a light source to the photo mask, and transferring a shape of the exposure patterns on the photo mask to the photoresist layer. The exposure patterns may be formed of opaque patterns or reflective patterns.
FIG. 1 is a schematic diagram of exposure equipment having a conventional transmissive photo mask.
Referring to FIG. 1, the exposure equipment may include a light source 10, and a transmissive photo mask 12 spaced apart from the light source 10. The transmissive photo mask 12 may have various shaped exposure patterns. The exposure patterns may be formed of opaque patterns 14. The exposure patterns may be divided into a high-density opaque pattern region 16a and a low-density opaque pattern region 16b according to a variation of a critical dimension (CD) corresponding to an interval between the opaque patterns 14. In other words, if the opaque patterns 14 have the same width, the interval between the opaque patterns 14 disposed in the high-density opaque pattern region 16a may be smaller than that between the opaque patterns disposed in the low-density opaque pattern region 16b. 
A masking blade 18 may be disposed between the light source 10 and the transmissive photo mask 12. The masking blade 18 may function to define an irradiation region of light on the transmissive photo mask 12.
A wafer stage 20 may be disposed at a position spaced apart from the transmissive photo mask 12. A wafer chuck 22 may be disposed on the wafer stage 20. The wafer chuck 22 may function to support a wafer 24. An optical system 26 may be disposed between the wafer chuck 22 and the transmissive photo mask 12. The optical system 26 may function to project light passing through the transmissive photo mask 12 onto the wafer chuck 22. The light passing through the optical system 26 may also pass through a light transmission adjustment mask 28 prior to entering the wafer chuck 22. The light transmission adjustment mask 28 may function to adjust an amount of light on the wafer chuck 22. The light on the wafer chuck 22 may be irradiated to a photoresist layer on the wafer 24 to form photoresist patterns thereon.
Transmissivity of the light passing through the transmissive photo mask 12 varies depending on a variation of the critical dimension of the exposure patterns. As a result, although the exposure patterns on the transmissive photo mask 12 may have the same width, the photoresist patterns formed on the wafer 24 may have different widths due to interference of the light generated while passing through the transmissive photo mask 12. For example, the photoresist patterns formed by the light passing through the high-density opaque pattern region 16a may be lower in resolution or contrast than the photoresist patterns formed by the light passing through the low-density opaque pattern region 16b. Consequently, the variation of the critical dimension of the exposure patterns may deteriorate the uniformity of the photoresist patterns formed on the wafer 24. In addition, the variation in the critical dimension of the exposure patterns may be created due to manufacturing tolerance of the exposure patterns.
The light transmission adjustment mask 28 may only adjust light intensity of the exposure equipment, regardless of the amount of the light passing through the high-density opaque pattern region 16a and the low-density opaque pattern region 16b, and thus, the adjustment mask 28 does not aid in solving the problems described above.
One conventional exposure apparatus includes a diffraction grating pattern plate in a conjugate relation with a reticle. However, when the grating pattern plate is used as a light transmission adjustment mask during an exposure process, a grating pattern on the grating pattern plate may be transferred onto a wafer.
FIG. 2 is a schematic diagram of exposure equipment having a conventional reflective photo mask.
The exposure equipment having the reflective photo mask may generally use extreme ultraviolet (EUV) as a light source. The EUV may be used as a light source, because short wavelength of the EUV is well absorbed, and therefore may be difficult to use in transmissive mask equipment.
Referring to FIG. 2, light may be irradiated to a reflective photo mask 32 from a light source 30 having a short wavelength, for example, EUV. The light reflected from the reflective photo mask 32 may be reflected by a plurality of mirrors M1, M2, M3 and M4, and then irradiated to a photoresist layer on a wafer 34. As a result, photoresist patterns may be formed on the wafer 34.
Exposure patterns may be formed on the reflective photo mask 32. The exposure patterns may be formed of a plurality of light absorbing layer patterns 36. The exposure patterns may be formed of a high-density light absorbing layer pattern region 38a and a low-density light absorbing layer pattern 38b. In example embodiments, according to a variation of a critical dimension of the exposure patterns, reflectivity of light reflected from the reflective photo mask 32 may vary. As a result, although the exposure patterns on the reflective photo mask 32 have the same width, the photoresist patterns formed on the wafer may have different widths due to dispersion of light generated while the light is reflected from the reflective photo mask 32. For example, because the light reflected from the low-density light absorbing layer pattern region 38b is larger in dispersion than the light reflected from the high-density light absorbing layer pattern region 38a, basic light intensity reflected from the reflective photo mask 32 may become different according to the density of the exposure patterns.
A difference in the basic intensity may be generated due to a variation of the critical dimension caused by manufacturing tolerance of the exposure patterns.
Consequently, the variation of the critical dimension of the exposure patterns may degrade uniformity of the photoresist patterns formed on the wafer 34.